Document processing devices, such as printers and copiers, include systems for transporting sheets of substrate media there-through. In order to increase the throughput of the device, the transport systems are designed to move the media rapidly along a media processing path. Transport systems may include wide transport belts or the media may be held against a large flat table for printing. One portion of the path which can negatively influence throughput is travel through a print zone in which an image will be imparted thereon. In the print zone, it is important that the movement of the sheet be precisely controlled to establish a high quality output. Moving the media into and out of the print zone in a controlled manner typically requires complicated transfers and involves various steps.
In color printing, color images are produced on a print media by repeatedly superimposing on a single print sheet different image layers or color image separations. This is typically accomplished by a process wherein subsequent image layers are formed on subsequent passes of the photoreceptor, each writing a different image layer during a single revolution of the photoreceptor (single pass) or by employing multiple exposure devices each writing a different layer on different photoreceptors. The toned developed image is then transferred from the photoreceptor(s) to paper or similar material, and the toner image is fixed by heat and pressure (fusing) to form a permanent copy.
In document processing devices designed for normal sized media substrates, proper registration of an image on media substrate is ensured through the use of charge-coupled devices (ccd). Ccd sensors are used to detect the position of the edge of a piece of paper, and relay that position to steering rollers which are moving the paper along the processing path. The steering rollers then appropriately adjust the movement of the paper to ensure the paper is engaged by the printer at the proper location for accurate registration.
This is mostly impossible with document processing devices which cater to over-sized media substrates, particularly those devices and systems which utilize platen carts on rails which are particularly heavy (upwards of 400 pounds). In these printers and systems it is difficult, if not impossible to adjust the location of the media substrate by adjusting the paper processing path on most axises. High speed inkjet marking devices for large sized cut sheets are particularly constrained using contemporary systems with regard to production output, media type and image quality. Also, such systems tend to be inflexible and difficult to change or modify, particularly with regard to their automated components.
Also, document processing devices, including high speed inkjet printing assemblies, include systems for transporting sheets of substrate media there-through. In order to increase the throughput of the device, the transport systems are designed to move the media rapidly along a media processing path. However, transporting large media such as cut sheets as large as 60″×40″, can be more difficult. Large media can be harder to hold flat across a large printing zone. Also, image quality can be an issue when printing across a large printing zone.
Contemporary large sheet printers use a multi-pass system in which a sheet of paper moves under fixed heads multiple times or the heads move over the paper multiple times. Multiple passes between the print heads and the sheet reduce productivity by slowing down production and tend to diminish image quality due to the difficulties in targeting the sheet in the desired location on different passes. It is accordingly critical to ascertain proper location of the media substrate relative to the platen cart, and have a system in place to properly adjust either the substrate location of the printer output in order to provide appropriate image on paper registration.
Accordingly, it would be desirable to provide a media transport system and method for accurately transferring an image onto a media substrate to permit high quality outputs.